Mixotrophic cultivation offers a promising pathway for high-density microalgae production, but the mechanisms by which different nitrogen sources regulate the energy flow of exogenous organic carbon and drive phenotypic trade-offs remain unclear. In this study, we used Tetradesmus obliquus as a model organism to systematically evaluate its growth kinetics, morphological plasticity, and photosynthetic performance under nitrate, ammonia, and urea conditions, with or without exogenous organic carbon glucose. Integrating logistic modeling and correlation network analysis, the results reveal that the nitrogen source acts as the core metabolic switch. Ammonium caused the lowest growth rate and carrying capacity, and this inhibition was not reversed by glucose supplementation. Conversely, the combination of nitrate and glucose acts merely as a growth kinetic accelerator, driving a rapid proliferation response (r-strategy) while maintaining stable colony formation. Notably, urea with glucose produced the highest carrying capacity and total biovolume, consistent with a K-strategy aimed at maximizing yield. This treatment also caused complete colony dissociation and an approximately fourfold increase in cell volume. The concomitant decline in Fv/Fm occurred alongside this dramatic cell hypertrophy, a pattern consistent with a possible geometric package effect rather than necessarily indicating severe cellular damage. These findings decode the complex energy-morphology-physiology coupling mechanism within microalgae, providing solid theoretical support for optimizing industrial nutrient strategies.

Artificial light at night (ALAN), intensified by coastal urbanization, is an emerging threat to coastal ecosystems. We used the rotifer Brachionus plicatilis and its prey Phaeocystis globosa as a model predator-prey system to examine rotifer life-history traits, predator-prey dynamics, and transcriptomic responses under varying ALAN intensities. ALAN altered maturation timing without affecting lifespan, and it reduced fecundity, population growth, and clearance rate, thereby delaying the depletion of P. globosa. Transcriptomic and network analyses showed that rotifers exposed to ALAN exhibited altered expression of candidate regulatory genes, including cytoskeleton-associated protein 5 (ckap5) and Raf proto-oncogene, serine/threonine kinase (raf) family members. These changes were associated with a CKAP5-associated microtubule module, RAF/PKA-related signaling, reproductive and cell-cycle-related pathways, and FoxO/autophagy-associated cellular-maintenance processes. These molecular responses provide potential regulatory clues for interpreting the phenotypic changes observed under ALAN exposure. Our findings help evaluate the potential effects of ALAN on zooplankton performance, and provide a scientific basis for assessing the environmental risks of coastal light pollution.

Arsenic risk in waters depends on chemical speciation, yet studies on host-associated microbiota to the in vivo detoxification mechanisms remain unclear. We exposed Daphnia magna for 21 days to inorganic arsenic at 2 mg/L with/without a broad-spectrum antibiotic cocktail that disrupts the gut microbiome. We assessed life-history traits, whole-body arsenic species by HPLC coupled to ICP-MS, and gut community composition by 16S rRNA gene sequencing with LEfSe and PICRUSt2 analyses. Both Arsenic and antibiotics alone impaired growth and reproduction, while co-exposure produced the strongest effects. Microbiome disruption increased total arsenic burden (∼14%) and shifted speciation away from detoxified end-products. Formation of arsenobetaine decreased by an order of magnitude, whereas dimethylarsinic acid approximately doubled. Under arsenic exposure alone, core taxa such as Aeromonas proliferated, accompanied by enrichment of predicted arsenic reductases and methyltransferases. Antibiotic treatment eliminated these taxa, favored Streptococcus, Methylophilus, and Veillonella, and suppressed predicted arsenic-processing functions. These results demonstrate that an intact Daphnia gut microbiome facilitates conversion of inorganic arsenic to less toxic organoarsenicals and mitigates toxicity. Microbiome integrity emerges as a practical control on arsenic fate and hazard in freshwater zooplankton, relevant to risk assessment under antibiotic co-contamination.

Perfluorooctanesulfonate (PFOS) is recognized as a major persistent pollutant due to its high environmental stability and bioaccumulation potential. This study investigated the effects of PFOS exposures (30, 60, and 90 μg/L) on growth, reproduction, oxidative stress, and energy metabolism in the marine water flea Diaphanosoma celebensis. PFOS exposure inhibited growth and fecundity in a concentration-dependent manner, with significant suppression observed at 60 and 90 μg/L. In addition to deleterious in vivo endpoints, the antioxidant enzymatic activities were significantly decreased, particularly at 90 μg/L of PFOS, after reaching its peak at 60 μg/L, suggesting that the antioxidant defense system may have reached its functional limit or been significantly compromised at the highest concentration. Lipid and glycogen analyses revealed concentration-dependent metabolic alterations. Specifically, at 30 μg/L, reductions in both triglyceride and fatty acid levels suggested enhanced lipid utilization for energy production. In contrast, exposure to 90 μg/L led to lipid accumulation and glycogen depletion, indicating impaired energy turnover. Gene expression analysis showed that CPT1A was upregulated at low PFOS concentrations, promoting fatty acid β-oxidation, whereas high PFOS concentrations upregulated G6Pase, MGAT, and DGAT while downregulating CPT1A and GYS, thereby favoring gluconeogenesis and lipid storage. This study demonstrates that PFOS induces concentration-dependent disruption of energy metabolism in D. celebensis, highlighting its potential ecological risks in aquatic environments.

Liquid crystal monomers (LCMs) are emerging contaminants in aquatic environments, but their compound-specific toxicity and sublethal effects in aquatic invertebrates remain insufficiently understood. In this study, we investigated and compared the toxic effects of three representative LCMs, EDPrB, tFPO-CF2-dF3B (tFPO), and BDPrB, using the freshwater water flea Daphnia magna. A 48-h acute toxicity test showed LC50 values of 55.9, 587.0, and 576.8 μg/L for EDPrB, tFPO, and BDPrB, respectively, indicating compound-dependent differences in acute toxicity. Based on these results, sublethal concentrations corresponding to 1/20 and 1/10 of each LC50 were selected to evaluate chronic and molecular deleterious endpoints. During a 28-day exposure, reproduction was markedly reduced in the B60 group, while the time to first brood was delayed in the EDPrB- and BDPrB-exposed groups. To evaluate oxidative stress-related responses, intracellular reactive oxygen species (ROS) levels, superoxide dismutase (SOD) and catalase (CAT) activities, and the expression of antioxidant-related genes were measured. EDPrB and BDPrB exposure increased several oxidative stress-responses, particularly in the B30 and B60 groups. Behavioral analysis showed that T60 exposure altered swimming distance and was accompanied by alterations in acetylcholinesterase (AChE) activity and AChE gene expression. In addition, P-glycoprotein (P-gp) and Multidrug resistance protein (MRP) activities were assessed to examine potential changes in multixenobiotic resistance (MXR)-mediated detoxification capacity following LCM exposure. Overall, these findings suggest that representative LCMs can affect reproduction, oxidative stress-related responses, behavior, and MXR-related deteoxification capacity in D. magna. This study provides integrated toxicity information for LCMs in a freshwater invertebrate model and supports the need for further ecological risk assessment of LCM contamination in aquatic environment.

Gradual salinization increasingly co-occurs with episodic heat stress, yet how these temporally asynchronous stressors jointly shape biotic responses remains unclear. Here, we tested whether prior salinity acclimation alters temperature and salinity interactions on Daphnia magna by comparing acclimated and non-acclimated individuals across five salinities (0, 0.06, 0.08, 0.10, 0.12 M) and three temperatures (20, 25, and 30 °C). In non-acclimated D. magna, warming and salinity synergistically impaired performance, reducing EC50 for offspring of the first brood and number of broods, and elevating integrated biomarker response (IBR) values under salinity stress. In contrast, salinity acclimation transformed this interaction into antagonism, with heat stress no longer exacerbating salinity induced damage or elevating IBR values. Salinity acclimation enhanced heat tolerance mainly at 0.08 M, where the change rate in the heat tolerance for reproductive traits, survival time, time to maturity, and spine length at maturity improved under warming (P < 0.001). Transcriptional and trait-gene correlations indicated a shift from an injury-linked, highly inducible state to a buffered state. In non-acclimated D. magna, combined stress synergistically upregulated osmoregulatory (Na+/K+-ATPase α/β), protein homeostasis (HSP70), and antioxidant (Cu/Zn SOD, CAT) genes. After acclimation, salinity still increased Na+/K+-ATPase α/β expression, but warming no longer amplified this response and instead dampened salinity-induced oxidative stress defenses. Gene expression was broadly negatively correlated with phenotype, but these correlations weakened after acclimation, supporting partial decoupling. Overall, salinity acclimation converts synergistic heat-salinity effects into antagonistic outcomes, highlighting the importance of exposure history and stressor timing for multiple-stressor risk assessment.

The pH of freshwater fluctuates in response to acid deposition and metabolic activity of algae, influencing cyanobacterial growth and trophic interactions. Although the effects of pH on cyanobacterial physiology have been widely studied, how pH regulates protozoan grazing and associated top-down control remains poorly understood. Therefore, this study simulated natural pH variability and possible acidification conditions in freshwater ecosystems, and systematically investigated the grazing effects of Paramecium multimicronucleatum on Microcystis aeruginosa over a wide pH gradient (pH 5.0–10.0). The acidic environment significantly inhibited the growth rate of M. aeruginosa and decreased the population size, while a neutral or alkaline pH had a positive effect. In grazing treatments, the specific growth rates and grazing rates of P. multimicronucleatum decreased with decreasing pH. However, P. multimicronucleatum effectively eliminated the populations of M. aeruginosa under all pH conditions tested in the experiment. This may be attributed to the combined effects of reduced grazing by P. multimicronucleatum and decreased growth of M. aeruginosa at lower pHs, while enhanced grazing at higher pHs strongly suppressed alkaline-adapted populations of M. aeruginosa. Consequently, the time required for P. multimicronucleatum to remove M. aeruginosa was not delayed significantly under water acidification. Overall, these findings highlight the broad pH tolerance of P. multimicronucleatum and its stable function of inhibiting harmful algae even under acidifying freshwater conditions.

Benzophenone-type UV filters (BPs) are widely used in personal care products and various industrial applications, resulting in their continuous release into aquatic environments. BPs have attracted significant attention as emerging contaminants because of their widespread use, structural diversity, environmental persistence, various exposure pathways, and adverse toxicological effects in aquatic organisms. Previous studies have largely focused on environmental occurrence and individual toxicological effects of BPs, whereas evidence regarding their interactions with multiple environmental stressors remains fragmented. Available evidence indicates that environmental factors and co-occurring contaminants can modify the environmental fate, bioavailability, bioaccumulation, and toxicity of BPs, resulting in antagonistic, additive, or synergistic effects depending on the stressor, organism, and exposure conditions. Therefore, this review describes the widespread distribution and toxicological effects of BPs in aquatic ecosystems, examining how environmental factors and co-occurring contaminants modify the environmental fate and toxicological effects of BPs under multi-stressor conditions. This review suggests that the ecological significance of BPs lies not only in their intrinsic toxicity but also in the way multi-stressor interactions modify their biological impacts, thereby defining directions for future ecological risk assessment.

Fine-scale prey patchiness is underexplored, yet theory predicts effects on trait variance. We tested these predictions in juvenile Scardinius erythrophthalmus reared for 46 days under homogeneous versus patchy distributions of live zooplankton prey, with prey inputs matched at session start to isolate spatial configuration from initial prey delivery. Under patchy supply, fish rapidly aggregated into prey-rich patches, creating strong foraging-rate (FR) contrasts between prey-rich and prey-poor locations; patchiness altered how FR scaled with prey density without a consistent increase in mean FR. Despite pronounced behavioural redistribution, cohort mean dry mass declined slightly under a near-maintenance ration, and endpoint central tendencies in body length and wet mass were similar between treatments. In contrast, standard metabolic rate (SMR), measured post-absorptively under standardized respirometry conditions, was higher in absolute terms in fish from the patchy treatment, while body-mass-corrected SMR overlapped strongly between treatments but showed increased inter-individual dispersion under patchiness. Patchiness also amplified dispersion in endpoint body-size traits, indicating greater physiological and developmental heterogeneity under spatially structured resource access. Together, these results show that prey patchiness can decouple foraging dynamics, baseline metabolic costs and body-size outcomes, with the dominant signature being increased within-cohort trait variance even when initial prey delivery is controlled.

Predation is an important selective pressure shaping phenotypic plasticity in aquatic organisms. As the key mediator between environmental changes and host physiology, gut microbiota and their metabolism play crucial roles in regulating host fitness. Although a few studies have extended the effects of predation risk on gut microbial composition, relatively little is known about whether and how the gut metabolite profiles are reshaped and linked to host defensive responses. This study integrated phenotypic assays, 16S rDNA sequencing and metabolomic analysis, systematically revealing the coordinated shifts in gut microbes and metabolites of Daphnia magna under fish kairomone exposure, which may be associated with D. magna's morphological and reproductive defences. Particularly, the enrichment of the indicator taxa Selenomonadaceae and Sporichthyaceae was negatively correlated with dAMP and adenine in the purine metabolism pathway, suggesting restricted nucleotide synthesis and ATP production. The resulting energy deficit may activate AMPK while inhibiting mTOR signalling, reallocating energy from somatic growth to reproductive investment. Moreover, Selenomonadaceae enrichment was linked to reduced PGD2 in the neuroactive ligand-receptor interaction pathway, potentially weakening Gs-cAMP-PKA signalling, suppressing cell proliferation and leading to a smaller body size of D. magna. These coordinated associations suggest a potential mediating role for gut microbe-metabolite interactions in the growth-survival trade-off of Daphnia under predation risk, which requires further experimental validation. These findings expand our understanding of host ecological adaptation from a gut microbial functional perspective.

Phytoplankton, as primary producers in aquatic ecosystems, serve as key indicators of water environmental stability through their community assembly and resource utilization strategies. However, their functional responses and biogeographical patterns in heterogeneous habitats created by artificial water diversion projects remain poorly understood. This study investigated the artificial channel in the Caichao Section of the Yangtze-to-Huaihe Water Diversion Project through seasonal surveys from 2023 to 2024, aiming to elucidate the compositional dynamics, resource use, community assembly, and spatial distribution of phytoplankton under different revetment structures (concrete-lined channel and composite caisson–rubble revetment). Results revealed a pronounced seasonal succession in phytoplankton community structure, with cell density peaking in summer 2024 (2.83 × 108 cells/L). Spatially, cyanobacteria dominated in the western concrete-lined channel, whereas the eastern composite-structure habitat exhibited co-dominance of Cyanobacteria, Chlorophyta, and Bacillariophyta, along with higher functional richness—highlighting the role of habitat heterogeneity in shaping functional diversity. Analysis of resource use efficiency revealed that biomass-based resource use efficiency (RUEB) was significantly positively associated with functional diversity and was higher in the concrete-lined channel. Community assembly demonstrated that stochastic processes predominated in the eastern composite-structure section, suggesting that revetment structures influence assembly through hydrological alterations and increased microhabitat complexity. The distance–decay exhibited seasonal fluctuations, with stronger spatial turnover during low-temperature periods. From a functional trait and community ecology perspective, this study elucidates the response mechanisms of phytoplankton to habitat heterogeneity in artificial channels, providing a theoretical basis for the ecological design and sustainable management of large-scale water diversion projects.

Beneficial bacteria-plant associations have attracted increasing attention for the remediation of heavy metal contamination. However, heavy metals often suppress key plant-growth-promoting traits in rhizobacteria, including indole-3-acetic acid production, thereby weakening the synergistic performance and overall efficiency of bacteria-plant system. Bacteria-semiconductor biohybrids provide an alternative strategy by enabling light harvesting and intracellular electron generation, which may influence bacterial metabolic activities. In this study, a metal-tolerant bacterial strain was employed to construct bacteria-CdS biohybrids through in situ conversion Cd²⁺ in the wheat rhizosphere, with the aim of enhancing indole-3-acetic acid-mediated bacteria-plant communication. The selected strain, Priestia sp. ZJT-3, predominantly formed CdS nanoparticles on the cell surface (37.4 nm in situ and 5.66 nm after extraction). The CdS exhibited a cubic crystal structure with characteristic (111), (220), and (311) planes and generated 1.088–2.069 μA cm-2 under illumination. Metabolomic analysis identified 936 metabolites that differed significantly between light and dark conditions in the bacteria-CdS biohybrids. Illumination increased extracellular IAA concentration from 4.983 to 7.723 mg L-1, which was associated with activation of the intracellular indole-3-acetonitrile and indole-3-acetamide pathways. Furthermore, the in situ formation of bacteria-CdS biohybrids increased wheat biomass and resulted in the lowest shoot Cd concentration (46.044 mg kg-1) compared to the control (56.635 mg kg-1). Collectively, these findings suggest a light-responsive plant-bacteria interaction framework that integrates cadmium conversion with auxin-related signaling and may contribute to safer crop production.

Acid deposition​​ ​​can cause​​ water acidification. As a critical abiotic factor, water pH determines ​​community structure​​ of plankton, including protozoan and cyanobacteria. Some species of protozoans​​ ​​exhibit high grazing efficiency against​​ Microcystis aeruginosa and are​​ ​​potential biological regulators​​ ​​of​​ harmful cyanobacterial blooms. Therefore, it is necessary to clarify the effectiveness of protozoa in controlling M. aeruginosa under the trend of water acidification. This study ​​systematically investigated​​ the ​​grazing effects​​ of Paramecium multimicronucleatum ​​on​​ M. aeruginosa ​​across a wide pH gradient​​ (pH 5.0–10.0), ​​simulating​​ the ​​natural pH variability​​ and ​​the possible acidification conditions​​ ​​in​​ freshwater ecosystems in the future. Results revealed that M. aeruginosa population exhibited significant a decline when the water pH was acidic, whereas neutral or alkaline pH promoted its ​​exponential growth​​ and ​​population stability. In the grazing treatments, the specific growth rate of P. multimicronucleatum decreased linearly with decreasing pH. Moreover, the grazing rate of P. multimicronucleatum decreased significantly as pH declined and tended to stabilize when pH was higher than 8. In addition, P. multimicronucleatum was able to completely eliminate M. aeruginosa population within eight days across all tested pH conditions​​, with​​ ​​no significant differences. This outcome can be attributed to the counteracted effect of the reduced grazing rate of P. multimicronucleatum and the decreased growth rate of M. aeruginosa at lower pH levels. Consequently, the time required for P. multimicronucleatum to remove M. aeruginosa did not delay significantly under water acidification. These findings suggest that P. multimicronucleatum can still effectively control M. aeruginosa population even under future scenarios of water acidification.

Gut microbiota influence the expression of traits during host growth and development, and are increasingly recognized as the critical driver of host fitness. However, their role in the host's inducible anti‐predator defense in response to predation pressure remains unclear. Here, we investigated how the assembly of the early‐life gut microbiota affects the induced anti‐predation morphological, behavioral, and life‐history defenses of Daphnia magna . The results show that different types of bacterial inoculations specifically altered the gut microbial community of D. magna and further mediated the differential expression of its morphological and life‐history defenses, rather than behavioral defenses, to cope with subsequent predation risk. Specifically, early life inoculation with probiotics such as Escherichia coli significantly enhanced the reproductive output and spine length of D. magna under subsequent predation risk, whereas early life inoculation with pathogenic bacteria such as Aeromonas hydrophila significantly reduced the body size, spine length, and reproductive output of D. magna under subsequent predation risk. Behavioral defense, that is, negative phototaxis, did not exhibit significant variation due to changes in the gut microbiota. Furthermore, the growth–survival trade‐off of D. magna under predation risk may be mediated by specific bacteria present in its gut microbiota, such as Staphylococcus . These results reveal the role of the gut microbiota in shaping prey defenses and deepen our understanding of host–microbiota co‐adaptation to complex environmental stressors.

Due to climate change and human activities, frequent temperature fluctuations and diverse nitrogen pollution occur simultaneously, which may have complex impacts on algae. This study examined the regulatory mechanisms of different nitrogen sources on the thermal adaptability of the freshwater alga Scenedesmus obliquus. The alga was cultivated under the combination of three temperature regimes (C: 24 degrees C, T1: 24 f 3 degrees C, T2: 24 f 6 degrees C) and three nitrogen sources (NaNO3, NH4Cl, CO(NH2)2), and a series of ecophysiological indicators and the related gene expression were measured. Results indicated that temperature fluctuations significantly inhibited algal growth, with inhibition intensifying as fluctuation magnitude increased. S. obliquus maintained the highest cell density and carrying capacity under NaNO3, followed by CO(NH2)2 and NH4Cl. Both nitrogen source and temperature fluctuation significantly affected Fv/Fm, Phi PSII, NPQ, but without interaction. Among three nitrogen sources, Fv/Fm decreased under temperature fluctuations, while Phi PSII increased (except for the T2-NaNO3 group). S. obliquus cultured in NaNO3 was dominated by multicellular colonies across three temperature regimes, whereas temperature fluctuations resulted in predominantly unicells in NH4Cl or CO(NH2)2. S. obliquus adapted to temperature fluctuations by synergistically upregulating the expression of photosynthesis, sugar metabolism, mitosis, and stress-responsive genes when NaNO3 was used as nitrogen source. With NH4Cl, it primarily activated stress-responsive genes under T1. Under CO(NH2)2 supply, it downregulated photosynthesis and mitosis related genes. These results suggest that nitrogen sources regulate the response of S. obliquus to temperature fluctuations, providing insights into phytoplankton adaptation under combined nitrogen and temperature fluctuations.

The interaction between temperature and precipitation greatly affects plant phenology. However, these effects can vary between additive, antagonistic, and synergistic, and it is not clear what determines these different outcomes. One hypothesis is that the effect on plant phenology varies with aridity and plant functional group. Here, we find support for this hypothesis using a global meta-analysis on the timing of leaf-out (2178 values from 55 experimental sites) and flowering (4027 values from 117 experimental sites). We find that, globally, the onset of leaf-out is more influenced by water availability than by temperature, while first flowering is more affected by temperature than by precipitation. On its own, warming advances leaf-out for all functional groups (except in semi-humid regions), whereas warming combined with decreased precipitation delays leaf-out in semi-arid regions. Warming also advances flowering across all functional groups, regardless of changes in precipitation and aridity. We observe synergistic effects of warming and precipitation on leaf-out for forbs in semi-arid regions, while antagonistic effects occur for grasses and sedges except in arid regions. Our findings suggest that considering drought tolerance or resistance of plants across ambient climates is critical for improving our understanding and predictions of how plant phenology responds to climate change.

This study aims to clarify whether two circular mitochondrial structures and gene order are conserved within and among species of the genus Brachionus, and to identify potential peculiarities associated with the extensive ecological niches occupied by different species. We analyzed the complete mitochondrial genomes of 23 Brachionus strains from 11 species, including three freshwater species and eight species from the brackish-water Brachionus plicatilis species complex. Results showed that all Brachionus strains exhibited conserved two circular chromosome: mtDNA-I, containing four protein-coding genes (PCGs), 13 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs); and mtDNA-II, containing eight PCGs and nine tRNAs. However, variation in gene arrangement was observed between species (e.g., cytochrome c oxidase rearrangement in freshwater B. calyciflorus) and strains within the B. plicatilis species complex (e.g., tRNA-L1, tRNA-L2, and tRNA-C rearrangements). Nucleotide diversity and nonsynonymous-to-synonymous substitution ratio analyses revealed higher sequence variability in NADH dehydrogenase genes (e.g., nad2, nad4, and nad5). These observations may reflect adaptive divergence of mitochondrial energy metabolism among Brachionus inhabiting different environments. Phylogenetic comparative models revealed that, similar to previous findings for the nuclear genome in the B. plicatilis species complex, mitochondrial genome size and features are correlated with organism body size across species.

Marine dinoflagellates are increasingly exposed to concurrent ocean warming and eutrophication; however, their responses to multiple concurrent stressors remain inadequately understood. Here, we investigated the individual and combined effects of elevated temperature (26 °C vs. 22 °C) and a high nitrogen-to-phosphorus ratio (180:1) on the harmful algal bloom-causing dinoflagellate Karenia mikimotoi during a 30-day exposure experiment. Elevated temperature and high N:P ratio, individually and in combination, significantly increased growth rate by 16-24 % relative to the control, while chlorophyll a (Chl a) content decreased by 22-29 %. Cellular particulate organic nitrogen (PON) content declined by 21-22 % under elevated temperature alone and in combination with a high N:P ratio, whereas particulate organic carbon (POC) content remained unchanged across all treatments. Interaction analyses revealed antagonistic effects of elevated temperature and high N:P ratio on growth rate, Chl a, and PON contents. Transcriptomic analyses showed that elevated temperature primarily upregulated genes associated with energy production and lipid biosynthesis, whereas a high N:P ratio enhanced the expression of genes involved in nitrogen assimilation and urea cycle-related pathways. Under combined stress, gene expression patterns indicated a transcriptionally inferred shift in energy allocation toward soluble sugar and lipid metabolism, accompanied by downregulation of urea cycle-related genes, suggesting a trade-off between energy conservation and nitrogen utilization. These results highlight the importance of antagonistic interactions between warming and nutrient imbalance in shaping the physiological and molecular responses of dinoflagellates, with implications for predicting harmful algal bloom dynamics under future ocean conditions.

The concomitant prevalence of toxic cyanobacteria blooms and plastic pollution in aquatic ecosystems is emerging as a pressing global water pollution dilemma. While toxic cyanobacteria and microplastics (MPs) can each independently exert significant impacts on aquatic biota, the magnitude and trajectory of the combined interactions remains rudimentary. In this study, we evaluated how MPs influences cyanobacterial stress on keystone grazer Daphnia, focusing on population, individual, biochemical and toxicogenomic signatures. We found that toxic Microcystis (TM) adversely affected the fitness of Daphnia populations (intrinsic rate of population increase), and these adverse effects were amplified in the presence of MPs. Through detailed observation, it was ascertained that MPs promoted the ingestion of TM, culminating in enhanced microcystin bioaccumulation. Using the Eco-Evo model, we found that there was potential absence of correlation between the MPs toxicity and the effect size of MPs on the TM. Utilizing gene set enrichment analysis (GSEA), we further identified a marked suppression of molecular pathways and entities crucial to individual growth and development in the TM-MPs consortium compared to exposure to TM alone. The present study provides important insights about the influence of MPs on cyanobacteria toxicity and the prediction the risk of harmful algal blooms in aquatic ecosystems.